As President & CEO of Seoul National University Bundang Hospital, Prof Junghan Song oversees his hospital’s lab, which currently uses mass spectrometry for routine clinical testing, including testing for vitamin D, one of the most important molecules in the human body. In this talk at the Re-imagining Mass Spectrometry Symposium, he outlines the pros and cons of various testing methods for vitamin D detection, the challenges of standardisation, and the possible use of bioavailable vitamin D as an alternative.